The nasty weather that stretched well into April provided the Bills' new defensive coordinator an additional excuse to stay indoors and become more familiar with his players and staff.

"One of the good things about being here in Buffalo is the weather was so bad that we had plenty of time as coaches to stay together," Schwartz said with a laugh, following a voluntary minicamp practice this week. "When the snow was rolling and it was 5 degrees outside, we were holed up in the room watching all their stuff from last year."

It was an invaluable experience for the defensive-minded specialist, who finds himself back in his element in Buffalo a few months after losing his job following a five-year stint as the Detroit Lions' head coach.

"You can spin coaching changes any way you want. The one thing I would say is the players do have a clean slate," Schwartz said. "They have to prove themselves. And I'm in the same boat. I've got to prove myself all over again. It's exciting. That'll bring out the best in players. It'll bring out the best in coaches."

Filling the vacancy after Mike Pettine left to take over the Cleveland Browns, Schwartz inherits a Bills defense that began shedding its once-porous and passive reputation by emerging as the team's strength last season.

While Buffalo (6-10) struggled on offense in large part because of rookie quarterback EJ Manuel's inconsistencies and injuries, the defense finished 10th in the NFL in yards allowed — the unit's best ranking in nine years. The Bills also finished second in the league with 23 interceptions and a franchise-record 57 sacks. And they had four defenders earn Pro Bowl selections, including tackle Marcell Dareus, who was added as an injury replacement.

The only area of concern was Buffalo's inability to stop the run. The Bills gave up 150 or more yards rushing six times, and finished 28th in allowing an average 129 net yards rushing per game.

Schwartz has a strong track record in devising schemes to stop the run. During his eight seasons as Tennessee's defensive coordinator, the Titans finished sixth or better in rushing yards allowed six times from 2001-08.

It's on Schwartz to build on that success with a unit that features a few new wrinkles at linebacker, where the team added Brandon Spikes and Keith Rivers in free agency, and was unable to re-sign three-time Pro Bowl safety Jairus Byrd.

Schwartz is Buffalo's fourth defensive coordinator in four seasons. He doesn't anticipate a difficult transition, even though he's making the switch to a 4-3 style of defense, and his philosophy is considered less aggressive than Pettine's pressure-the-passer approach.

Schwartz is keeping much of the same play-calling terminology. And he said the switch to four linemen and three linebackers shouldn't be regarded as significant, because his and Pettine's defenses share similar elements.

"No, we're not going to be read-and-react. We're going to attack guys," Williams said. "Now, if we do it with four rushers, five rushers or six, that'll have to be game-planned. But we're going to be on the move. And we're going to attack."

Spikes liked what he's seen after two weeks of minicamp practices.

"We've still got a long way to go, but if we can take these necessary steps, I think we can be great this season and shock the world," said Spikes, who was signed in part because of his reputation as a run-stuffer during his first four seasons in New England.

"I take that personally. If you can stop the run, you can make them one-dimensional," Spikes said. "I think this season there'll be some eye-openers."